voltage regulator help

Discussion in 'The Projects Forum' started by markosillypig, Nov 27, 2009.

  1. markosillypig

    Thread Starter Active Member

    Jul 21, 2008
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    hi all i have an led circuit that requires a 14 volt 300 Ma power supply
    has any one got a scamatic or a design of one that i can use i have a power supply of 18V 500Ma that i will be using
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    The LM317 is an adjustable regulator. Get a data sheet to see how to use one. Your 18 volt source is adequate to power the regulator for your lower output. Be sure to get a heat sink for the 317, as it will be dissipating just over one watt of heat.
     
  3. SgtWookie

    Expert

    Jul 17, 2007
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    Marko,
    Post your circuit of how you have connected the LEDs.

    There may be an easier way to do it than using an additional regulator.
     
  4. markosillypig

    Thread Starter Active Member

    Jul 21, 2008
    184
    0
    hi sgt
    here is the problem i have got a set of old disco lights
    8 channel pick attached i have removed the circuit whitch works ok but the problem is i do not have a 14v 300Ma psu for it so my intention is to build one i have a 15v 500Ma supply but i do not want to distroy the circuit if 15volts will be too much fotr it

    i intend to make a star blanket for the festive season with the 8 channels
     
  5. SgtWookie

    Expert

    Jul 17, 2007
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    Your 15v supply - is it regulated, or is it an unregulated wall-wart type?

    What voltage does the 15v supply output when there is no output load connected to it? That will be a big clue.
     
  6. SgtWookie

    Expert

    Jul 17, 2007
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    If it turns out to be a voltage regulated power supply (15v out with no load), you could simply use one or two 1N540x or 1N400x series diodes to drop about 0.7v (one diode) to 1.4v (two diodes in series) between the +V output and your project's +V supply input. This would give you a 14.3v output or a 13.6v output.

    Try two diodes in series first.

    Don't use 1N4148/1N914 diodes; they won't handle the current.
     
  7. markosillypig

    Thread Starter Active Member

    Jul 21, 2008
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    the 15v supply is kicking out 14.96v without any load on it
     
  8. SgtWookie

    Expert

    Jul 17, 2007
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    OK, try the two diodes (1N540x or 1N400x) in series first. If it works like that, use it that way.
     
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